1. Field of the Invention
The present invention generally relates to a laser array device and laser array control method, and more particularly to a laser array device and laser array control method which detects independently respective optical outputs of lasers of a laser array and controls the laser array driving.
2. Description of the Related Art
In recent years, with the progress of optical-communication technology, the information processing devices are connected together by the optical fiber cables, and the communication between the information processing devices has come to be performed by transmitting and receiving the optical signals via the optical fiber cables.
The laser array device is used to output the laser beam from the laser light source to the optical fiber cable according to transmission information. The laser array device is usually equipped with a laser safety circuit. This laser safety circuit is provided to control the output of the laser array so that the intensity of the laser beam outputted from the laser array device satisfies the requirements of the laser safety standards.
FIG. 1 shows the composition of a conventional laser array device. As shown in FIG. 1, the conventional laser array device comprises the laser array driver IC 100, the laser array 300, the monitor photodiode MD1, and the monitor photodiode MD2.
The laser array driver IC 100 and the monitor photodiode MD1 constitute the first detection and control loop of the laser safety circuit, and the laser array driver IC 100 and the monitor photodiode MD2 constitute the second detection and control loop of the laser safety circuit.
The laser array 300 comprises the communication laser array 310, the monitoring laser 301, and the output control laser 302.
The monitor photodiode MD1 detects the laser beam outputted from the monitoring laser 301, and feeds back the detected information to the laser array driver IC 100.
The monitor photodiode MD2 detects the laser beam outputted from the output control laser 302, and feeds back the detected information to the laser array driver IC 100.
In the example of FIG. 1, the communication laser array 310 is provided to output the laser beams of six channels (or six bits) for the sake of convenience of description. In the conventional laser array device, the communication laser array 310 is controlled by carrying out the monitoring of the laser beams outputted from the monitoring laser 301 and the output control laser 302 by means of the first and second detection and control loops.
The laser array driver IC 100 controls the intensity of each of the six-channel laser beams outputted from the communication laser array 310. That is, the input data of the six channels according to transmission information which should be transmitted is inputted into the laser array driver IC 100, and the laser array driver IC 100 drives each of the lasers of the communication laser array 310 according to the input data of the six channels. The laser beams outputted from the lasers of the communication laser array 310 are outputted to the six optical fiber cables, respectively.
In the case of the conventional laser array device, when the performance of the monitoring laser 301 degrades or the laser output efficiency thereof falls, the control information to increase the intensity of each of the laser beams outputted from the communication laser array 310 is sent from the monitor photodiode MD1 to the laser array driver IC. In such a case, the laser output of the communication laser array 310, which operates normally, may exceed the reference level of the laser-beam intensity of the laser safety standards.
In order to prevent this problem, the second detection and control loop, which comprises the monitor photodiode MD2 and the output control laser 302, is provided, and, when the intensity of the output laser beam of the output control laser 302 which is detected by the monitor photodiode MD2 exceeds the reference level, the laser array driver IC 100 detects the excessive laser-beam intensity, and performs the control of stopping the laser output of the communication laser array 310.
However, when both the monitoring laser 301 and the output control laser 302 break down, the control function to stop the laser output exceeding the reference level does not work in the conventional laser array device. That is, in this case, the excessive laser beam may be outputted from the communication laser array 310.
As described above, the conventional laser array device is configured so that the monitoring laser 301 and the output control laser 302 separate from the communication laser array 310 are arranged, and the monitor photodiodes MD1 and MD2 corresponding to these exclusive-use lasers are arranged. For this reason, if any of the exclusive-use lasers 301 and 302 and the photodiodes MD1 and MD2 break down, sufficient countermeasures against that case are not taken.
Moreover, when any of the exclusive-use lasers 301 and 302 and the photodiodes MD1 and MD2 break down, the oscillation of all the lasers of the communication laser array 310 may be stopped by the control information so that the whole system carrying the laser array device stops, even if the lasers of the communication laser array 310 are not out of order.